Method of placing explosive charges

ABSTRACT

Seismic energy for geophysical prospecting is provided by drilling a shot-hole to a selected depth using a cutting tool such as a hydraulic jet nozzle or a downhole drill motor attached to a non-rotating, continuous flexible spooled conduit; pumping a liquid explosive and detonating means actuatable from the earth surface down the conduit, through the cutting tool and into the shot-hole; withdrawing the conduit and cutting tool from the shot-hole; and detonating the explosive.

United States Patent [191 Adair et al. I

[ Apr. 16, 1974 METHOD OF PLACING EXPLOSIVE CHARGES [75] Inventors:James C. Adair, Bellaire; Robert R.

Luke, Houston, both of Tex.

[73] Assignee: Shell Oil Company, Houston, Tex.

[22] Filed: July 27, 1972 [21] App]. No.: 275,857

[52] US. Cl 175/1, 175/67, 175/237 [51'] Int. Cl E21b 7/18 [58] Field ofSearch 102/20, 21, 21.8; 181/.5 XC; 175/1, 57, 67, 122, 162, 220, 237,317

. [56] References Cited UNITED STATES PATENTS 2,880,966 4/1959 Blount 175/1 2,883,154 4/1959 Daniel 3,075,463 l/l963 Eilers et al 102/21 X3,100,542 8/1963 Stark 175/1 3,590,738 7/1971 Holzman.... 102/213,702,635 11/1972 Farr ,175/1 X Primary Examiner-David H. BrownAttorney, Agent, or Firm-Tom M. Moran; Harold L. Denkler [57] ABSTRACTSeismic energy for geophysical prospecting is provided by drillingashot-hole to a selected depth using a cutting tool such as a hydraulicjet nozzle or a downhole drill motor attachedto a non-rotating,continuous flexible spooled conduit; pumping a liquid explosive anddetonating means actuatable from the earth surface down theconduit,,through the cutting tool and into the shot-hole; withdrawingthe conduit and cutting tool from the shot-hole; and detonating theexplosive.

5 Claims, 4 Drawing Figures METHOD PLACING EXPLOSIVE CHARGES BACKGROUNDOF THE INVENTION l. Field of the Invention This invention relatesgenerally to the art of forming and loading shot-holes; and, moreparticularly, to a method of forming a shot-hole and loading it with anexplosive charge to be used as a source of seismic energy forgeophysical prospecting.

2. Description of the Prior Art In acquiring seismic data forgeophysical prospecting, it is a common practice to detonate anexplosive charge at a subsurface location in a shot-hole. The explosioncreates shock waves which travel downwardly through the earth. Portionsof the shock waves are reflected back towards the earths surface as thewaves intersect planes of contact between various earth formations.These reflected waves are detected by sensing apparatus atthe surface.The recorded waves may subsequently be analyzed to provide informationas to the subsurface geological structure of the area tested.

A significant part of the cost of acquiring such seise mic data isexpended in drilling shot-holes and loading these holes with explosive.For example, the cost of a typical seismic crew may be on the order of$100,000 per month. It is common for such a crew to spend as much as 45percent of their time in the field drilling and loading shot-holes.Therefore, it can be seen that any substantial savings in the timerequired to provide loaded shot-holes can result in a significantdecrease in the cost of acquiring seismic information.

To this end, a number .of methods have been sug gested for loadingshot-holes through in-place drill pipe. This has the advantage ofreducing loading time by eliminating the need for pulling the shot-holedril ling equipment from the hole before loading the hole with anexplosive charge. It also has the advantage of substantially eliminatingthe chances of shot-hole cavein prior to loading. Such cave-ins areoften encountered when placing the charge through loose, unconsolidatedsoils such as sandy or muddy soils.

For example, US. Pat. No. 3,590,738 .teaches sealing the lower end of arigid drill pipe with a removable cover; driving the pipe toa desireddepth in an earth formation, preferably with sonic means; and loweringan explosive charge into the hole on a detonation wire which is attachedat a point just above the top of the pipe to support means that is justlarge enough to pass through the pipe with enough frictional engagementto retain the end of the wire above the surface of the ground as thepipe is pulled up over the wire and support means. The pipe is thenpulled away from the removable bottom cover and extracted from the hole.A somewhat similar system is disclosed by US. Pat. No. 3,434,549 whichteaches using a mechanical cutting element with a releasable latch meansthrough which an explosive may be lowered into the borehole.

Both of these prior art methods have the disadvantage of requiring anumber of time consuming manipulative steps at the earth surface as eachstep of the respective processes is carried out. That is, workmen at thesurface are required to prepare the shot-hole drilling equipment fordrilling the hole, drill the hole, disassemble the drilling equipmentfrom the pipe string at the surface, lower the charge into the pipe, andthen raise the pipe from the hole. If the hole is drilled deeper thanthe lift height of whatever lifting mechanism is used at the surface, itis necessary to uncouple and rack one or more joints of drill pipe asthe pipe is extracted from the hole.

SUMMARY OF THE INVENTION We have now discovered a method for drillingand loading shot-holes which comprises the steps of attaching an earthboring means to a spooled flexible conduit at least as long as thedesired depth of the shot-hole; ad-

vancing the earth boring means and the attached flexible conduit intothe earth to form the shot-hole; pump- The earth boring means may be anyboring means A suitable for drilling a hole using a non-rotating stringof pipe. For example, it may be a mechanically cutting bit rotated by adown-hole motor, such as a down-hole mud turbine driven by fluid pumpedfrom the surface through the drill pipe. Or the hole may be drilled byreverse circulation where loose material, such as mud or sand, is suckedfrom the'hole through the drill pipe by forcing liquid or air down aseparate conduit to a point above a rotating bit and then up the drillpipe to carry debris from the hole. In a preferred embodiment, theshot-hole is drilled using a hydraulic jet bit of a type which bores theshot-hole through the action of high pressure fluid impinging upon theearth formation to be cut. The bit may cut solely by hydraulic jet meansor may be combined with mechanical cutting elements suitable for cuttingformations which are highly resistant to the jet action of the bit,

Detonator means for igniting the liquid explosive can be pumped into thewell through the flexible drill pipe. Preferably the pump means whichdelivers fluid to the bit or other cutting element is operativelyconnected to a manifold means through which both the'liquid explosiveand the detonator may be inserted into the stream of flowing fluid byappropriately adjusting one or more valves in the manifold means.

In a preferred embodiment, a hydraulic jet bit is provided with afrangible plug which is blown from the bit to provide a passagesufficiently large for the detonator means to be emitted from the bitupon the application of sufficient pressure drop across the frangibleplug. This pressure drop may be achieved by temporarily plugging thenozzles of the hydraulic jet bit as by inserting a plugging means intothe drill pipe through the flow manifold and pumping the plug means downthe drill pipe into contact with thenozzles. In one embodiment the plugmeans comprise fracture sealing balls which seal off the nozzles of thebit thereby increasing the pressure drop across the plug means.

The detonator can be one which is remotely actuatable, e.g., one whichis actuated via detonation wires which couple it to .a detonationcontroller at the surface. The detonator is preferably pumpedinto thewell through the spooled drill pipe. The upper end of the detonator wireis preferably attached to a means of relatively small surfacearea forfrictionally engaging the interior of the pipe string to retain theupper end of the wire above the earth surface as the pipe is withdrawnfrom the shot-hole in a manner similar to that taught by US. Pat. No.3,590,738.

It is advantageous in some cases to enlarge the lower end of theshot-hole prior to inserting the liquid explosive into the shot-hole inorder to provide a less linear and more point-shaped shot. In manyformationsthis may be achieved by circulating fluid through thehydraulic jet bit while maintaining the bit at a constant depth at thebottom of the shot-hole to wash out an enlarged hole. In otherformations it may be' necessary to provide remotely actuatable reamingmeans for enlarging the hole. One method for doing this is to direct thehole sealed by the frangible plug means of the hydraulic jet bit at anangle such that when the plug is removed a jet of fluid'will emerge fromthe bit at such an angle that it contacts the sidewall of the shot-hole.In this way, the shot-hole may be enlarged prior to placement of theexplosive charge.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view', partiallyin cross-section, of a preferred apparatus for use in practicing themethod of this invention.

FIG. 2is a .vertical cross-section of a hydraulic jet nozzle of a typewhich may be effectively used in the DESCRIPTION OF A PREFERREDEMBODIMENT Referring to FIG. 1, we see a shot-hole drilling apparatuswhich may be mounted on a truck 11. The apparatus comprises a spooled,continuous flexible conduit 12 such as ,a hose or a flexible metallicdrill pipe. An earth boring means such as hydraulic jet nozzles 13 isattached to the conduit 12. .The conduit 12 is spooled on a drum 14which is coupled to suitable means (not shown) for spooling andunspooling the conduit 12 by turning the drum. Guide means such aspulley 15 and conduit guide 16 arepreferably provided for controllingthe direction of movement of the conduit as it is unspooled.

In the embodiment of FIG. 1, energy is applied to the face of aformation 17 to be cut by pumping a fluid from a fluid source (notshown) through pump 18 and into the flexible conduit 12. This fluidpasses down the conduit 12 and is emitted through one or more nozzles 19in the hydraulic jet nozzle 13. Preferably, at least one of thesenozzles is canted so as to create a rotational thrust on the hydraulicjet nozzle 13. A swivel joint 20 or other rotatable connection couplesthe hydraulic jet nozzle 13 to the flexible conduit 12. Therefore, asfluid is emitted through canted nozzle 19, the nozzle head 13 turnscausing the jet emitted from the nozzles 19 to traverse the face of theformation 17.

In a preferred embodiment, the guide 16 comprises a large diameterconduit 21 slideably mounted on the base of the truck 11. The conduit 21is preferably provided with a fluid return outlet 22 for carryingretuming drilling fluid away from a shot-hole 23. The guide 16 isadvantageously connected to a lowering means such as hydraulic means 24which may be used to seat 4 the guide 16 firmly in the hole drilling iscommenced. The guide 16 comprises a bowl portion 26 of diametersufficient to accommodate passage of the hydraulic jet nozzle 13. Thebow 26 is advantageously tapered to hold a set of guide slips 27. Theslips 27 preferably have a tapered outer face for seatingly engaging thetapered bowl 26 and have a curved inner surface 28 which defines anopening of decreasing cross-section passing from the top to the bottomof the slips. The curved face 28 of the slips 27 is sized to slidinglyengage conduit 12 and hold it vertical as it enters shot-hole 23. Tofurther ensure the initial straightness of the shot-hole 23, it ispreferred to use a short segment of rigid pipe 29 immediately above thehydraulic jet nozzle 13. This section is preferably on the order of 5 to10 feet long. As pipe segment 29 passes through guide slips 27, it isheld in the vertical position by the slips 27.

FIG. 2 shows a hydraulic jet nozzle head 13 of a type which may beadvantageously used in the practice of this invention. The bottom of thenozzle 13 comprises a port or opening 30 of diameter sufficient to allowpassage of an explosive detonating means. This opening 30 is closed witha frangible plug 31 which may be expelled from the opening 30 uponapplication of a sufficient pressure drop across the face of thehydraulic jet nozzle 13. Such a pressure drop may be achieved by rapidlyincreasing the rate of flow through the pumps 18 and nozzle head 13.Alternatively, pressure drop may be increased by sealing the ports 32 ofthe nozzles 19 of the nozzle head 13. This may be accomplished bypumping a nozzle shut-off means down the conduit 12 and into contactwith nozzle ports 32. For example, a number of fracture sealing balls 33may be injected into the flowing fluid stream down stream of the pump18. When these balls reach the nozzle head 13' they will lodge in theports 32 and plug these ports. This will cause an increase in pressurein the interior of the nozzle head 13 which will result in the expulsionof plug3l from opening 30.

Liquid explosive and detonating means may be pumped into the shot-hole23'through the opening 30 in the nozzle head 13. FIG. 3 illustrates apreferred means for delivering a detonating means 35 attached to adetonating wire 36 to the bottom of the shot-hole. A pulling member,such as a brush 37, is attached to the lower end of wire 36 to pull thewire 36 through the conduit 12 as fluid is pumped down the conduit 12.The bristles of the brush 37 are preferably longer than the radius ofthe conduit 12 and should be sufficiently flexible to allow the brushesto pass through the reduced diameter opening 30in the bottom of nozzlehead 13.

The upper end of the wire 36 is preferably attached to a support means38 which engages the conduit 12 with enough friction to retain the endof the wire above the surface of the ground as the pipe is pulled upover the wire and the support means, but with insufiicient friction tocause the wire to be withdrawn from the shot-hole 23 as the flexibleconduit 12 is removed from the hole. The support means should allowfluid to pass so that brushes 37 can be pumped downconduit 12. Forexample, the support means may be a scratcher which comprises aplurality of scratcher arms such as stiff wires 39 that engage theinterior of conduit 12 while still allowing fluid to pass. The supportmeans 38 is advantageously sized to pass through the opening 30 in thenozzle 13 upon upward flexing of the wires 39.

earth surface 25 before shot- FIG. 4 schematically shows a manifoldmeans 40 of a type which may be used to sequentially insert sealingballs 33, detonating means 35 and liquid explosive into the shot-hole23. The respective materials are held in chambers 41-43. Byappropriately opening the valves of the manifold 40 any one of thechambers 41 through 43 may be emptied into the conduit 12. Thedetonating wire 36 may be wound on a spool 44 rotatably mounted insidehousing 45 of chamber 42. As the brushes 37 pull the wire 36 into theconduit 12, the wire is drawn off the spool 14. The supportmeans 38 canbe releaseably attached to spool 44 with means such as a thin wire orstring (not shown) which breaks under tension when the wire 36 is fullyunwound from the spool 44.

To form and load a shot-hole 23 according to the method of thisinvention using the apparatus of the Figures, guide means 16 andhydraulic jet nozzle 13 are lowered into contact with earth surface 25.Fluid is then pumped through the conduit 12 and nozzle head 13 to formshot-hole 23. As the nozzle head 13 progresses into earth formation 17the drum 14 is turned to unspool conduit 12.

When the desired depth of shot-hole is reached, the valves of manifold40 are appropriately adjusted to pump sealing balls 33 from chamber 41down conduit 12 to seal ports 32 in nozzle 13. This increases thepressure in nozzle 13 causing plug 31 to be blown therefrom. A suitableliquid explosive, such as a nitromethane based liquid explosive of thetype described in US. Pat. Nos. 3,659,652 and 3,633,324, is then pumpedfrom chamber 43 of manifold 40 down conduit 12 through nozzle 13 andinto' the shot-hole 23. A remotely actuatable detonator 35 is pumpedfrom chamber 42 of manifold 40 through the conduit 12 and nozzle 13 intothe shot-hole adjacent the liquid explosive. Conduit 12 is thenwithdrawn from the shot-hole 23 by respooling the conduit on the drum14. This leaves a loaded shot-hole ready for detonation upon receipt ofan appropriate signal. According to one preferred embodiment, prior topumping-liquid explosive into the shot-hole, after the desired depth hasbeen obtained, fluid is circulated through the hydraulic jet nozzlewhile maintaining the conduit 12 stationary in the shot-hole 23. Thiswill enlarge the bottom portion of the shothole and thereby provide ashot cavity shaped more like a point source than a line source.

We claim as our invention:

1. A method of forming and loading a shot-hole comprising the steps of:

attaching an earth boring means to a spooled flexible conduit at leastas long as the desired depth of the shot-hole; advancing the earthboring means and attached flexible conduit into the earth to form theshot-hole; pumping a liquid explosive into the shot-hole through theflexible conduit to load the shot-hole; and withdrawing the flexibleconduit and attached earth boring means from the loaded shot-hole.

2. The method of claim 1 including the steps of:

pumping into the shothole a detonator wire longer than the shot-hole isdeep attached at its lower end to a detonating means and at its upperend to a support means for frictionally slideably supporting the upperend of the wire within the flexible conduit above the earth surface asthe flexible conduit is withdrawn from the shot-hole.

3. The method of claim 2 including the step of opening a port in theearth boring means of diameter sufficient to allow the detonating meansto pass through the port and into the shot-hole means before pumping thedetonator wire into the shot-hole.

4. The method of claim 3 wherein the step of opening a port in the earthboring means comprises increasing the pressurewithin the earth boringmeans to blow a plug from the wall thereof.

5. The method of claim 4 wherein the step of increasing the pressure inthe earth boring means comprises pumping one or more fracture sealingballs down the flexible conduit and into the earth boring-means.

1. A method of forming and loading a shot-hole comprising the steps of:attaching an earth boring means to a spooled flexible conduit at leastas long as the desired depth of the shot-hole; advancing the earthboring means and attached flexible conduit into the earth to form theshot-hole; pumping a liquid explosive into the shot-hole through theflexible conduit to load the shot-hole; and withdrawing the flexibleconduit and attached earth boring means from the loaded shot-hole. 2.The method of claim 1 including the steps of: pumping into the shot-holea detonator wire longer than the shot-hole is deep attached at its lowerend to a detonating means and at its upper end to a support means forfrictionally slideably supporting the upper end of the wire within theflexible conduit above the earth surface as the flexible conduit iswithdrawn from the shot-hole.
 3. The method of claim 2 including thestep of opening a port in the earth boring means of diameter sufficientto allow the detonating means to pass through the port and into theshot-hole means before pumping the detonator wire into the shot-hole. 4.The method of claim 3 wherein the step of opening a port in the earthboring means comprises increasing the pressure within the earth boringmeans to blow a plug from the wall thereof.
 5. The method of claim 4wherein the step of increasing the pressure in the earth boring meanscomprises pumping one or more fracture sealing balls down the flexibleconduit and into the earth boring means.